Maria T. Lazaro

Exogenous and evoked oxytocin restores social behavior in the Cntnap2 mouse model of autism

Mice carrying a genetic mutation that causes autistic symptoms show improved sociability after being treated with oxytocin, a hormone promoting mothering and trust. Going Social Oxytocin—a hormone that promotes mothering, trust, and social bonding in animals—seems a likely treatment for the social isolation of individuals on the autism spectrum, but tests in humans have generally proved disappointing. To delve deeper into how oxytocin affects autism symptoms, Peñagarikano et al. created a mouse mimic of one type of genetic autism, cortical dysplasia and focal epilepsy (CDFE) syndrome, by deleting the gene that is mutated in human patients. Unlike normal mouse-loving mice, CDFE mice were asocial, showing no preference for other mice over objects, but this deficit was reversed by giving them oxytocin. Further, revving up the sluggish production of their own oxytocin in the paraventricular nucleus in the hypothalamus also improved sociability. Most hopeful for patients, the authors found that giving young CDFE mice multiple doses of oxytocin just after birth produces a long-lasting improvement in oxytocin brain levels and sociability. Mouse models of neuropsychiatric diseases provide a platform for mechanistic understanding and development of new therapies. We previously demonstrated that knockout of the mouse homolog of CNTNAP2 (contactin-associated protein-like 2), in which mutations cause cortical dysplasia and focal epilepsy (CDFE) syndrome, displays many features that parallel those of the human disorder. Because CDFE has high penetrance for autism spectrum disorder (ASD), we performed an in vivo screen for drugs that ameliorate abnormal social behavior in Cntnap2 mutant mice and found that acute administration of the neuropeptide oxytocin improved social deficits. We found a decrease in the number of oxytocin immunoreactive neurons in the paraventricular nucleus (PVN) of the hypothalamus in mutant mice and an overall decrease in brain oxytocin levels. Administration of a selective melanocortin receptor 4 agonist, which causes endogenous oxytocin release, also acutely rescued the social deficits, an effect blocked by an oxytocin antagonist. We confirmed that oxytocin neurons mediated the behavioral improvement by activating endogenous oxytocin neurons in the paraventricular hypothalamus with Designer Receptors Exclusively Activated by Designer Drugs (DREADD). Last, we showed that chronic early postnatal treatment with oxytocin led to more lasting behavioral recovery and restored oxytocin immunoreactivity in the PVN. These data demonstrate dysregulation of the oxytocin system in Cntnap2 knockout mice and suggest that there may be critical developmental windows for optimal treatment to rectify this deficit.

The Autism Related Protein Contactin-Associated Protein-Like 2 (CNTNAP2) Stabilizes New Spines: An In Vivo Mouse Study

The establishment and maintenance of neuronal circuits depends on tight regulation of synaptic contacts. We hypothesized that CNTNAP2, a protein associated with autism, would play a key role in this process. Indeed, we found that new dendritic spines in mice lacking CNTNAP2 were formed at normal rates, but failed to stabilize. Notably, rates of spine elimination were unaltered, suggesting a specific role for CNTNAP2 in stabilizing new synaptic circuitry.

Transcriptome Profiling of Peripheral Blood in 22q11.2 Deletion Syndrome Reveals Functional Pathways Related to Psychosis and Autism Spectrum Disorder.

Background 22q11.2 Deletion Syndrome (22q11DS) represents one of the greatest known genetic risk factors for the development of psychotic illness, and is also associated with high rates of autistic spectrum disorders (ASD) in childhood. We performed integrated genomic analyses of 22q11DS to identify genes and pathways related to specific phenotypes. Methods We used a high-resolution aCGH array to precisely characterize deletion breakpoints. Using peripheral blood, we examined differential expression (DE) and networks of co-expressed genes related to phenotypic variation within 22q11DS patients. Whole-genome transcriptional profiling was performed using Illumina Human HT-12 microarrays. Data mining techniques were used to validate our results against independent samples of both peripheral blood and brain tissue from idiopathic psychosis and ASD cases. Results Eighty-five percent of 22q11DS individuals (N = 39) carried the typical 3 Mb deletion, with significant variability in deletion characteristics in the remainder of the sample (N = 7). DE analysis and weighted gene co-expression network analysis (WGCNA) identified expression changes related to psychotic symptoms in patients, including a module of co-expressed genes which was associated with psychosis in 22q11DS and involved in pathways associated with transcriptional regulation. This module was enriched for brain-expressed genes, was not related to antipsychotic medication use, and significantly overlapped with transcriptional changes in idiopathic schizophrenia. In 22q11DS-ASD, both DE and WGCNA analyses implicated dysregulation of immune response pathways. The ASD-associated module showed significant overlap with genes previously associated with idiopathic ASD. Conclusion These findings further support the use of peripheral tissue in the study of major mutational models of diseases affecting the brain, and point towards specific pathways dysregulated in 22q11DS carriers with psychosis and ASD.

The utility of rodent models of autism spectrum disorders.

PURPOSE OF REVIEW This review discusses the ways that rodent models of autism spectrum disorders (ASDs) have been used to gain critical information about convergent molecular pathways, the mechanisms underlying altered microcircuit structure and function, and as a screen for potential cutting edge-treatments for ASDs. RECENT FINDINGS There is convergent evidence that impaired developmental pruning of connections may be a common finding among several mouse models of ASDs. Recent studies have uncovered impaired autophagy by pathological mTOR activation as a potential contributor to microcircuit dysfunction and behavior. ASD-related disinhibition and exaggerated synaptic plasticity in multiple distinct circuits in cortex and reward circuits in striatum also contribute to social dysfunction and repetitive behaviors. New exciting molecular therapeutic techniques have reversed cognitive deficits in models of ASD, indicating that mouse models could be used for preclinical translational studies of new treatments. SUMMARY Rodent models of ASDs coupled to new emerging technologies for genome editing, cell-specific functional and structural imaging, and neuronal activity manipulation will yield critical insights into ASD pathogenesis and fuel the emergence of new treatments.

Overexpression of calcium-activated potassium channels underlies cortical dysfunction in a model of PTEN-associated autism

Significance Advances in human genetics have identified many gene alterations that cause autism, but how these mutations lead to cortical dysfunction is not understood. Mutations in the gene phosphatase and tensin homolog on chromosome ten (PTEN) cause autism and intellectual disability. We have discovered that single-copy deletion of Pten results in overexpression of the small-conductance calcium-activated potassium channel in cortical neurons. This overexpression leads to decreased sensitivity of cortical neurons to incoming inputs. In vivo, this diminished excitability leads to decreased primary visual cortical responsiveness to visual stimuli. We hypothesize that diminished cortical responses in primary sensory regions lead to poor recruitment of secondary sensory cortices, leading to sensory processing deficits. Our findings identify a unique target for potential pharmacological intervention. De novo phosphatase and tensin homolog on chromosome ten (PTEN) mutations are a cause of sporadic autism. How single-copy loss of PTEN alters neural function is not understood. Here we report that Pten haploinsufficiency increases the expression of small-conductance calcium-activated potassium channels. The resultant augmentation of this conductance increases the amplitude of the afterspike hyperpolarization, causing a decrease in intrinsic excitability. In vivo, this change in intrinsic excitability reduces evoked firing rates of cortical pyramidal neurons but does not alter receptive field tuning. The decreased in vivo firing rate is not associated with deficits in the dendritic integration of synaptic input or with changes in dendritic complexity. These findings identify calcium-activated potassium channelopathy as a cause of cortical dysfunction in the PTEN model of autism and provide potential molecular therapeutic targets.

Clinical and Neurobiological Relevance of Current Animal Models of Autism Spectrum Disorders

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by social and communication impairments, as well as repetitive and restrictive behaviors. The phenotypic heterogeneity of ASD has made it overwhelmingly difficult to determine the exact etiology and pathophysiology underlying the core symptoms, which are often accompanied by comorbidities such as hyperactivity, seizures, and sensorimotor abnormalities. To our benefit, the advent of animal models has allowed us to assess and test diverse risk factors of ASD, both genetic and environmental, and measure their contribution to the manifestation of autistic symptoms. At a broader scale, rodent models have helped consolidate molecular pathways and unify the neurophysiological mechanisms underlying each one of the various etiologies. This approach will potentially enable the stratification of ASD into clinical, molecular, and neurophenotypic subgroups, further proving their translational utility. It is henceforth paramount to establish a common ground of mechanistic theories from complementing results in preclinical research. In this review, we cluster the ASD animal models into lesion and genetic models and further classify them based on the corresponding environmental, epigenetic and genetic factors. Finally, we summarize the symptoms and neuropathological highlights for each model and make critical comparisons that elucidate their clinical and neurobiological relevance.

Rescue of the Functional Alterations of Motor Cortical Circuits in Arginase Deficiency by Neonatal Gene Therapy

Arginase 1 deficiency is a urea cycle disorder associated with hyperargininemia, spastic diplegia, loss of ambulation, intellectual disability, and seizures. To gain insight on how loss of arginase expression affects the excitability and synaptic connectivity of the cortical neurons in the developing brain, we used anatomical, ultrastructural, and electrophysiological techniques to determine how single-copy and double-copy arginase deletion affects cortical circuits in mice. We find that the loss of arginase 1 expression results in decreased dendritic complexity, decreased excitatory and inhibitory synapse numbers, decreased intrinsic excitability, and altered synaptic transmission in layer 5 motor cortical neurons. Hepatic arginase 1 gene therapy using adeno-associated virus rescued nearly all these abnormalities when administered to neonatal homozygous knock-out animals. Therefore, gene therapeutic strategies can reverse physiological and anatomical markers of arginase 1 deficiency and therefore may be of therapeutic benefit for the neurological disabilities in this syndrome. SIGNIFICANCE STATEMENT These studies are one of the few investigations to try to understand the underlying neurological dysfunction that occurs in urea cycle disorders and the only to examine arginase deficiency. We have demonstrated by multiple modalities that, in murine layer 5 cortical neurons, a gradation of abnormalities exists based on the functional copy number of arginase: intrinsic excitability is altered, there is decreased density in asymmetrical and perisomatic synapses, and analysis of the dendritic complexity is lowest in the homozygous knock-out. With neonatal administration of adeno-associated virus expressing arginase, there is near-total recovery of the abnormalities in neurons and cortical circuits, supporting the concept that neonatal gene therapy may prevent the functional abnormalities that occur in arginase deficiency.

Lung and heart-lung transplantation in pulmonary arterial hypertension

Background Real use of lung (LT) and heart-lung (HLT) transplantation in pulmonary arterial hypertension (PAH) is unknown. The objectives were to describe the indication of these procedures on PAH treatment in a national cohort of PAH patients, and to analyze the potential improvement of its indication in severe patients. Methods Eligibility for LT/HLT was assessed for each deceased patient. Incident patients from REHAP diagnosed between January 2007 and March 2015 and considered eligible for LT/HLT were grouped as follows: those who finally underwent transplantation (LTP) and those who died (D-Non-LT). Findings Of 1391 patients included in REHAP, 36 (3%) were LTP and 375 (27%) died. Among those who died, 36 (3%) were D-Non-LT. LTP and D-Non-LT were equal in terms of age, gender, and clinical status. Ten percent of those who died were functional class I-II. Patients functional class IV were less likely to undergo LT (8.3% LTP vs. 30.6% D-Non-LT, p = 0.017). Patients with idiopathic and drug/toxin-associated PAH were more likely to undergo LT (44.4% LTP vs. 16.7% D-Non-LT, p = 0.011). Conclusions The present results show that the use of LT/HLT could double for this indication. Relevant mortality in early functional class reflects the difficulties in establishing the risk of death in PAH.

Reduced prefrontal synaptic connectivity and disturbed oscillatory population dynamics in the CNTNAP2 model of autism

Loss of function mutations in CNTNAP2 cause a syndromic form of autism spectrum disorder (ASD) in humans and produce social deficits, repetitive behaviors, and seizures in mice. Yet, the functional effects of these mutations at the cellular and circuit level remain elusive. Using laser scanning photostimulation, whole-cell recordings, and electron microscopy, we found a dramatic decrease in functional excitatory and inhibitory synaptic inputs in L2/3 medial prefrontal cortex (mPFC) of Cntnap2 knock-out (KO) mice. In accordance with decreased synaptic input, KO mice displayed reduced spine and synapse densities, despite normal intrinsic excitability and dendritic complexity. To determine how this decrease in synaptic inputs alters coordination of neuronal firing patterns in vivo, we recorded mPFC local field potentials (LFP) and unit spiking in head-fixed mice during locomotion and rest. In KO mice, LFP power was not significantly altered at all tested frequencies, but inhibitory neurons showed delayed phase-firing and reduced phase-locking to delta and theta oscillations during locomotion. Excitatory neurons showed similar changes but only to delta oscillations. These findings suggest that profound ASD-related alterations in synaptic inputs can yield perturbed temporal coordination of cortical ensembles.

Correction: Lung and heart-lung transplantation in pulmonary arterial hypertension

[This corrects the article DOI: 10.1371/journal.pone.0187811.].